Conventionally, a humidity controller apparatus which controls the humidity of air using an adsorbent material has been known. For example, in a humidity controller apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-22206, first and second process subject air are distributed in a hollow casing by first and second fans. In the casing, distribution routes for the process subject air are switched, and adsorption and desorption of moisture is alternately carried out by each adsorption element. In the above humidity controller apparatus, the first adsorption element and the second adsorption element are alternately used to carry out humidification and dehumidification of process subject air which is to be supplied to an indoor space.
In the above humidity controller apparatus, an air filter is generally provided in order to prevent a foreign material from intruding into a device contained in the casing. Conventionally, various structures have been employed as to the arrangement of an air filter. For example, a humidity controller apparatus wherein a suction opening provided on a side surface of a heat exchanger contained in the casing is directly covered with an air filter as in the air filter disclosed in Japanese Laid-Open Utility Model Publication No. 60-178735 has been known. With this, intrusion of a foreign material into the heat exchanger which would be greatly affected by the intrusion of a foreign material can be prevented. However, with such a countermeasure, a distribution route in the casing for process subject air which extends up to the heat exchanger is greatly affected by intrusion of a foreign material.
In the above humidity controller apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-22206, for example, any one of a pair of side walls of the casing is provided with a suction opening for introducing first process subject air and an outlet opening for expelling second process subject air, while the other side wall is provided with a suction opening for introducing the second process subject air and an outlet opening for expelling first process subject air. In the humidity controller apparatus having such a structure, it is necessary to provide an air filter in the vicinity of each suction opening as shown in, for example, Japanese Laid-Open Patent Publication No. 4-350443 in order to remove the foreign material from the process subject air at the time when the process subject air flows into the casing.